1. Field of the Invention
The invention relates to a pneumatic discharge apparatus for a stripping centrifuge.
2. Description of the Prior Art
A pneumatic discharge apparatus is shown in West German Pat. No. 20 56 893. The discharge apparatus described therein is in the form of an oscillating stripping device, which must be moved up and down in order to discharge all of the material contained in the stripping centrifuge. In addition to this axial motion, the stripping head located inside the centrifuge drum at the frontal end of the discharge line must be adjusted in the radial direction also, in order to remove as much as possible of the material to be stripped, deposited on the inside of the drum. In the course of the oscillating axial motion and the radial advance movement superposed on it, substantial sealing problems arise, caused among others, by abrasion in the bearings of the discharge apparatus. This sealing problem is of extraordinary importance particularly in pharmaceutical and chemical fields because even one drop of oil penetrating through a leak into the material to be stripped, for example, a medicine, could render the entire charge of the drug in the drum useless.
The known pneumatic discharge apparatus has a further disadvantage, namely, only a low overall discharge efficiency is obtained due to the back-and-forth motion required. Furthermore, as the material to be stripped cannot be removed completely from the drum, the remaining residual layer is being set by the constant sweep of the blade, particularly in the case of a high residual humidity. Consequently, this residual layer filters out very poorly during subsequent charges and may have to be removed manually.
Finally, in view of the time consuming oscillating motion, only a relatively low volume of the material may be discharged in unit time.